Digestion in the Stomach

If the stomach does not function properly, then the rest of the digestive system will become compromised, and over the long term, cause a decline to our general health and well being”.

The “Gastric” phase of digestion (stomach specific), initially begins with the anticipation of food via smell or sight, and then by the chewing action of the mouth.

This triggers the release of the hormone Gastrin, which acts to release gastric juice containing HCL, Pepsinogen, Intrinsic Factor, mucus and water. Gastrin also stimulates gastric motility, blood flow to the stomach, hepatic (liver) bile secretion, pancreatic enzymes and bicarbonate release (which we will discuss at the “Intestinal” phase of digestion, in a later post).

We have already mentioned HCL or stomach acid in previous posts, but why would its long term reduction be a bad thing?

Well its main digestive role is to begin the digestion of proteins and disassociate vitamins & minerals, for absorption in the intestines. As protein is derived from the Greek word “proteos” meaning “primary” or “first place”, this gives an indication of its importance to our physiological function. Add the vitamins and minerals into the mix and any reduction would seriously hamper our nutritional status.

HCL is also vital as a defensive barrier against pathogens entering through the mouth, and any reduction in its output compromises this barrier both upstream, and downstream, with regard to the bacterial colonies (microflora), resident in both the small and large intestines.

Indeed the downstream effects may be even more significant over the long term, as not only will this affect the composition of the microflora – which in turn profoundly influences the nervous, endocrine (hormones) and immune system of the host - YOU! - but also the magnitude and quality of the digestive secretions coming from the gall bladder, pancreas and small intestinal wall.

We have not even arrived at the Intestinal part of digestion yet, but suffice to say that the gall bladder, pancreas and small intestine itself, affect all aspects of both digestion and absorption, so any reductive factor cannot be positive.

Therefore we should never underestimate the importance of maintaining a proper HCL response, in relation to our all round good health.

Protein digestion actually commences in the stomach, through the release of an inactive enzyme called Pepsinogen, which is activated into the enzyme Pepsin by the ph of the HCL.

Another important nutrient – vitamin B12 – begins its digestion in the stomach by binding with a substance called Intrinsic Factor, that is released from the parietal cells in the stomach wall.

Vitamin C, Iron, Magnesium and Calcium, all undergo transformation in the acidity of the stomach, making them easier to absorb in the small intestine.

Water is released to further dissolve the bolus, whilst mucus is added to protect the stomach from being digested, by the mixture of protein degrading enzymes and HCL.

Smooth muscle contractions in the stomach wall churn the bolus further into a substance called chyme, which is then steadily released into the duodenum (1st part of the small intestine).

This is done in a time controlled manner, so as not to overload the small intestine, to allow for proper digestion to occur.

It is also worth noting that carbohydrates pass through the stomach quickest, with proteins and fats taking longer. This is to allow glucose to be delivered for energy requirements, and for optimum digestion of the proteins to occur in the acidic environment of the stomach.

There is only a limited digestion of fats within the stomach (performed by gastric lipase), due to the fact that fats require emulsification from bile, which occurs in the small intestine.

Carbohydrate digestion stops in the stomach, as the amylase (carbohydrate) enzymes are inactive below a certain ph, favouring the alkaline environment of the small intestine. This is another reason that they pass through the fastest.

Finally, it is vital to understand that although the actions of the stomach are regulated by a variety of feedback mechanisms, it is the nervous system that has the most profound influence.

This is because the mechanical and enzymatic action of the stomach, is primarily triggered by the peripheral nervous system (PNS ) via the vagus nerve, which then releases gastrin.

During periods of chronic stress, we are constantly using the opposing arm of the nervous system called the sympathetic nervous system(SNS – fight or flight), when there should normally be a balance between the two.

As one switches off the other, eating our food in a more sympathetic (stressed out) state, would act as a dampener to the digestive quality of the stomach.

Therefore this is a major reason why combating stress is so important for both our digestive and general health, and why eating in a rush or “on the go” is a very bad idea.

So as you see from this basic description on the functions of the stomach, we can now begin to understand why any disruption in its performance, could have much farther reaching consequences to our general long term health.

NEXT POST: The Intestinal Phase – The Secondary Digestive Organs

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